1. Field of the Invention
This invention relates generally to internal combustion engines, and more particularly to such engines having rotary valves for controlling intake and exhaust communication with the power cylinders.
2. Description of the Prior Art
The theoretical advantages offered by internal combustion engines having rotary valves, over engines having conventional reciprocal poppet-type valves, have long been recognized. Rotary valve engines enable a significant reduction in moving parts over their poppet-type valve counterparts, proving inherent increased engine reliability thereover, smoother and quieter engine operation and reduced maintenance requirements. While several design variations of such engines have appeared in the prior art, they have not been generally accepted by manufacturers or the purchasing public because of the practical problems associated with those designs, which problems have typically outweighed the theoretical advantages of such engines. Such practical problems have typically included sealing problems, distortion, lubrication, tooling, difficulty of repair and maintenance and the cost and facility of manufacture of such rotary valve engines.
Internal combustion engines are well known in the art and generally comprise one or more compression chambers, each having intake and exhaust ports, a spark plug or other appropriate ignition element for igniting a combustible gaseous mixture within the chamber, a piston element for compressing the gaseous mixture within the compression cylinder and a crankshaft or other appropriate output drive means for transmitting the combustion energy into usable mechanical output energy. Combustible gaseous mixtures are provided from an intake manifold to the intake port of the cylinder and spent exhaust gases are expended from the exhaust port of the cylinder to an exhaust manifold by valve means which regulate and control the timed opening and closing of the intake and exhaust ports of the respective cylinders of the engine. "Rotary valve" embodiments of such valve means, to which this invention applies, include at least one rotatable member which selectively controls opening and closing of the intake and exhaust ports of the compression cylinder and selectively places the respective intake and exhaust ports of said cylinders in fluid communication with the intake and exhaust manifolds respectively of the engine.
Prior art rotary valve engines can be generally classified, according to he basic operative structure of the rotating valve member portion of the engine, into two groups or types of valve structures: (1) those in which the rotating valve member defines a plurality of fluid flow passageways which extend diametrically through the rotating valve member, for directly transmitting intake and exhaust gases respectively between the intake and exhaust manifolds and the intake and exhaust ports of the compression cylinder portions of the engine; and (2) those in which the rotating valve member defines longitudinally extending internal fluid flow passageways therein which provide fluid flow communication through single strategically located openings in the outer shell portion of the rotating valve member between the intake and exhaust manifolds and the intake and exhaust ports respectively of the compression cylinders of the engine.
U.S. Pat. No. 3,948,227 to Guenther, represents a rotary valve engine configuration of the first above-described type. A rotary valve of this type requires transfer (during the intake cycle) of the combustible fuel mixture from the intake manifold or carburation apparatus of the engine to the intake port of the compression cylinder -- all during that time interval in which the respective diametrically extending valve inlet passageways of the rotating valve member are in simultaneous "alignment" with the diametrically opposed intake manifold source and the respective intake ports of the cylinders. By their operative nature, such valve structures represent inefficiency in their transfer of intake gases to the cylinders, since the combustible intake mixture must travel through the full diameter of the rotating valve member during the short "alignment". The initial delay in the receipt of intake gases by a cylinder during the intake cycle is basically the rate of flow of the gas mixture through the rotating valve member times the length of the fluid passageway through the rotating valve member. Further, with such rotating valve structures, it is difficult to pressurize the gaseous mixture in the intake manifold so as to speed the intake procedure, for increasing the horsepower of the engine. While several such pressurization techniques have been attempted in the past, they have generally been difficult to implement and have not proved to be very efficient in operation. Further, most of such attempts have been directed more toward the concept of vaporization or atomizing the fuel within the carburetor than toward actual positive pressurization of the gaseous mixture to the combustion cylinders.
U.S. Pat. Nos. 2,853,980 and 3,871,340 to Zimmerman, represent rotary valve engine configurations typical of the second above-described type. With this second type of rotary valve engine configuration, since the intake gases are always present within a longitudinal portion of the rotating valve member, there are virtually no delays associated with the transfer of combustible gases to the respective cylinders during the "intake" cycle. Upon alignment of the intake valve opening in the rotating valve member with the intake port of the respective compression cylinder, the combustible gases pass directly from the rotating valve member into the compression cylinder, with the only delay associated with the gas transfer therebetween being represented by the propagation delay of the gaseous mixture passing through the thickness of the outer wall of the rotating valve member. While rotary valve apparatus of the second type have generally proved to be more efficient than the first-described type of rotary valve apparatus with respect to their fluid transfer properties, their construction has generally been more complex and costly, and have presented more problems with the forming of reliable seals between various portions of the valve apparatus. In particular, mounting of the rotating valve member of the "second" type of valve assembly, within the engine head, has typically not enabled easy maintenance or replacement of the rotary valve portion of the apparatus or of associated internally disposed seal members. Further, with both of the above-described prior art structures, intake of the combustible mixture into the compression cylinder has depended only upon the suction or "draw" of the cylinder itself, caused by the partial vacuum created with the cylinder when the piston moves in the "downward" direction during the intake portion of the cycle. As the volume of available combustible intake mixture increases, for example with the second above-described type of apparatus, the practical effect of the "draw" is significantly reduced, basically leaving an inefficient gravity flow intake system.
The present invention overcomes the above-mentioned problems associated with both the first and second basic embodiments of the rotary valve engine structures. While the structural operation of this invention is basically of the second above-described type, it is configured in a manner which offers a high degree of simplicity and ease of maintenance and repair and which maximizes efficiency and horsepower rating of the structure without sacrificing seal reliability between the various portions of the valve apparatus.
While the present invention will be described with respect to the preferred embodiment of a rotary valve engine, it will be obvious to those skilled in the art in light of this disclosure, that other variations of the rotary valve member, the seal forming elements, the positive fluid-flow enhancing means, the exhaust feedback means and the material used herein, can be configured within the spirit and intent of this invention.